More than one-in-five Minnesotans under age 65 had health problems last year that would give them a personal stake in the debate over repealing and replacing the federal health law.

That's the conclusion of a report released Monday from the California-based Kaiser Family Foundation that estimated about 744,000 Minnesotans under 65 had a health problem that would block them from coverage if insurance companies reverted to rules that were in place before the Affordable Care Act (ACA).

The estimate is much bigger than the number with health problems who have found commercial coverage under the health law, because it includes people with "declinable" preexisting conditions with other types of insurance, such as coverage through employer groups.

Republicans in Washington D.C., have proposed repealing the ACA, and several replacement plans would direct people lacking health insurance to coverage through high-risk pools.

"We don't know a lot of the details yet of what a repeal-and-replace plan is going to look like," said Cynthia Cox, a researcher with the foundation. "High risk pools … might still be able to protect people with preexisting conditions in a different way than the ACA does, but a lot of that is going to come down to funding," Cox said. "If the high-risk pools aren't adequately funded ... [coverage might have] much higher premiums or exclusions based on your preexisting condition."

Before the ACA, preexisting-condition exclusions were a factor in Minnesota's individual market, where fewer than 300,000 people currently buy coverage. It's the market for people who are self-employed and those who don't get coverage from an employer or government program.

People denied coverage in Minnesota's individual market used to turn to the state's high-risk pool, which charged premiums that were up to 25 percent above the market rate. Some saw premium reductions when major health law changes kicked in for 2014, but prices have jumped since then and consumers next year face tight limits in their choice of doctors and hospitals.

Before the ACA, individual markets across the country were subject to "medical underwriting," where insurers looked at an applicant's health status, history and other factors to determine whether and under what terms to provide coverage, according to the report. The study looked at those old rules and 2015 data to estimate in each state the number of residents with conditions that might prevent them from buying an individual policy.

The report found the rate of people with declinable preexisting conditions in Minnesota is 22 percent, which was the lowest rate in the nation. West Virginia's rate at 36 percent was highest among states.

Southern states that see higher rates of heart disease, diabetes and obesity tended to have a higher share of residents with declinable preexisting conditions, Cox said. Nationally, about 52.2 million people have declinable preexisting conditions, or 27 percent of the nonelderly population. "The fact that tens of millions of people have preexisting conditions underscores the importance of paying attention to the details of repeal-and-replace plans," Cox said.

The estimates include people with health problems who aren't currently covered through individual policies, Cox said, because they might eventually need access to the market due to a job change or early retirement.

It has become clear that repealing the Affordable Care Act will be taken up quickly in Congress, although there is expected to be a multiyear delay before it is replaced.

Republican replacement plans rely on state-run high-risk pools, which can provide subsidized insurance to people who are declined, but have in the past included high premiums and deductibles, exclusions for some preexisting conditions and limits on medical coverage. The Republican plan also has a "continuous coverage" provision, which would ensure that people can't get big premium hikes if they get sick — as long as they stay insured.

One question dangling over the promise to keep providing insurance to people regardless of their health history has been how to do so without one of the most unpopular provisions of the law — the mandate that people carry insurance. To avoid simply charging the sickest people very high premiums, insurers need a mix of healthy and sick people to sign up.

Kristine Grow, a spokeswoman for America's Health Insurance Plans, a lobbying group for insurers, said in an e-mail that there is a need for alternative incentives for people to get and remain covered, mentioning that waiting periods or penalties for people who have had a break in coverage "could go a long way to avoiding even higher premiums and fewer choices for everyone."

The Washington Post contributed to this story.

Twitter: @chrissnowbeck